The long-term goals of this proposed research are to determine the mechanism(s) of insulin action in the regulation of glycogen metabolism and cardiac performance and to determine how diabetes mellitus affects these processes. Specifically, I will study the regulation of cardiac glycogen metabolism and mechanical performance in isolated perfused hearts (non-working and working) from normal, alloxan diabetic, and spontaneously diabetic (Bio Breeding Laboratory) rats. The site(s) of the defect in insulin-regulation of cardiac glycogen synthesis and the mechanism of insulin activation of glycogen synthase will be determined at the molecular level by: 1) purification of glycogen synthase from normal and diabetic rat hearts, 2) purification of glycogen synthase phosphatase from rat hearts, 3) preparation of an antibody to rat heart synthase phosphatase, and 4) utilization of these purified preparations to determine the site(s) and cause(s) of the defect, and the mechanism of insulin action. Tissue enzymatic activities to be studied are glycogen synthase (D and I), synthase phosphatase along with its inhibitor(s), cyclic AMP-dependent synthase kinase, and cyclic AMP-independent synthase kinase. Metabolites to be assessed are glucose-6-phosphate, glucose-1-phosphate, uridine diphosphate glucose, adenosine triphosphate, cyclic AMP and glycogen. Physical performance will be studied in hearts from chronically diabetic rats (1 to 4 months) which have been untreated, treated with suboptimal concentrations of insulin, and treated with optimal concentrations of insulin to determine the effects of duration of the disease and treatment on pathological developments. Coronary flow, aortic output, aortic pressure development, and ventricular pressure development will be studied in isolated working rat hearts under aerobic, anoxic and ischemic conditions without and with hormonal (epinephrine, insulin and glucagon) intervention. This study should provide new information on the mechanism of insulin to activate glycogen synthase, the defect in this activation by insulin in the diabetic, and the effects of chronic diabetes on mechanical performance of the heart.